[PATCH] D37142: clang-format: [JS] simplify template string wrapping.

Daniel Jasper via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Mon Aug 28 03:19:07 PDT 2017

djasper added inline comments.

Comment at: lib/Format/ContinuationIndenter.cpp:1139
+  // On lines containing template strings, propagate NoLineBreak even for dict
+  // and array literals. This is to force wrapping an initial function call if
mprobst wrote:
> djasper wrote:
> > This is not the right way to implement this:
> > 
> > - This is a static computation that we could do ahead of time. Doing it inside the combinatorial exploration of solutions is a waste.
> > - You are doing this always, even in code that doesn't have template strings or isn't even JavaScript.
> > - This can lead to unexpected behavior if the template string is in a completely unrelated part of the statement. E.g.
> > 
> > 
> >   someFunction(`test`, { ... });
> > 
> > will be formatted differently from
> > 
> >   someFunction('test', { ... });
> Ack. Do you have suggestions?
> I could introduce a `bool  ParenState::NoLineBreakMustPropagate;` that controls this behaviour.
That, too, would create a significant memory and runtime overhead to everyone just to fix this rather minor formatting detail.
If we were to set MatchingParen correctly to match up "${" to "}", we could measure the respective length and at a very early state (mustBreak()) decide that we need a line break between "${" and the corresponding "}". Now setting that correctly might be hard. Maybe it is ok, to linearly scan in that case as we would only do that if we actually find a template string ending in "${" and the distance to the "}" is usually short.


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